In conventional reflector antenna systems, the narrow patterns in the farfield of the reflector are brought to a focus where a single feed horn or a group of feed horns are placed to capture or sample the reflected energy from the system. To sample the field in different positions, the feed horn or group of feed horns can be moved in the focal plane of the antenna system so as to scan the antenna beams. The beam positions in the far-field move in a nominally linear relation to the feed position shift (for small angles).